ABSTRACT
ABSTRACT: Codes of practice aim at assuring structures having the risks acceptable to the public and the minimum total costs over a design working life. However, current codified criteria for structural design correspond to a broad range of reliability levels, specified for dissimilar reference periods even though their recalculation for different periods is uncertain due to an unknown dependence of failure events in time. The submitted approach to specifying target reliability levels is based on probabilistic risk optimization considering the objective function as a sum of various costs including the effects of time to failure and discounting. An example of probabilistic optimization of a generic structural member shows the effect of considered input parameters. It appears that the optimum reliability level expressed by reliability index depends primarily on the structural costs, failure costs and costs for improving structural safety. Less significantly it seems to be affected by the time to failure and the discount rate.
